Method of manufacturing centrifugal pump casings



Sept. 16, 1969 D, M RRI 5R 3,466,724

METHOD OF MANUFACTURING CENTRIFUGAL PUMP CASINGS Filed March 9, 1967 3 Sheets-Sheet 2 JPA CERJ awn? MAI/V0861 /2 //v PdJ/T/O/Y ATTORNE Y P 6, 1969 H. o. MORRIS, 5R 3,466,724

METHOD OF MANUFACTURING CENTRIFUGAL PUMP CASINGS Filed March'9, 1967 3 Sheets-$heet 5 flared J M/f/J, J):

' INVEN TOR ATTORNE Y United States Patent US. Cl. 29156.4 6 Claims ABSTRACT OF THE DISCLOSURE A method of manufacturing centrifugal pump casings having a layer of corrosive-resistant material covering the entire internal surface of the casing, including the ring recesses which receive the rotor assembly.

This invention relates to a method of manufacturing centrifugal pumps. More particularly, it relates to a method of manufacturing centrifugal pumps having a layer of corrosive resistant material in the form of epoxy resin covering the entire internal surface of the casing of the pump. It has particular reference or utility in connection with pumps having upper and lower sections made of cast iron and in which each of the sections has at least one semi-annular recess, which recesses together form an annular opening in the assembled condition and wherein the pump has a rotor assembly a portion of which is adapted to be received in the annular opening in the assembled condition.

One of the reasons which causes corrosion of certain metals in centrifugal-type pumps is that unlike metals in the presence of an electrolytic fluid, such as water, form a galvanic cell with one of the metals acting as the anode and is thereby destroyed by the electrolytic action thereon. Normally, the housing for centrifugal-type pumps is cast iron, and therefore acts as the anode and is thereby corroded more readily than other parts of the pump.

It is therefore desirable to have a centrifugal pump wherein the entire insides of the cast iron pump casing is completely coated and thereby electrically insulated from the electrolyte or otherwise separated from the corrosive fluid being pumped therethrough.

'In the past, certain coatings have been used to coat portions of the inside of centrifugal pumps, but no method has heretofore been devised whereby the entire internal surface of the casing could :be coated with a corrosive resistant material such as epoxy resin and with a minimum of time and eifort.

In the normal manufacture of centrifugal pumps of the foregoing type wherein protective coatings were not provided to the entire internal surface of the pump casing, the pump had a case body which was cast to the desired general size and thereafter the ring recesses were milled by machines to the exact specification of the rotating assembly which was to be mounted therein. This machining operation is expensive and time consuming.

It is therefore the object of this invention to provide an improved method of manufacturing centrifugal type pumps wherein the entire inside surface of the pump casing is provided with a coating of corrosive resistant material in the form of a polymerized epoxy resin.

Briefly stated, this invention is a method of manufacturing a centrifugal pump having a layer of corrosive resistant material covering the entire internal surface of the casing of the pump and wherein the pump has upper and lower sections made of cast iron, each of the sections having at least one semi-annular recess, which recesses together form an annular opening in the assembled condition, and wherein the pump has a rotor assembly a portion of which is adapted to be received in the annular opening in the assembled condition.

The method comprises the steps of casting the upper and lower sections with oversized, semi-annular recesses. Thereafter, each of the semi-annular recesses is initially coated with a layer of unpolymerized epoxy resin, with the thickness of the layers being greater than the radial distance between the annular opening and the portion of the rotor assembly positioned therein in the assembled condition. Thereafter the rotor assembly is placed in one of the sections in the rotating position and the other section of said casing is mounted thereover, with spacing means between the sections. The sections are then drawn together against the spacing means, thereby pressing the layers of epoxy resin in said recesses to the desired thickness. The sections are then separated after the epoxy resin has polymerized to a hardened condition. The balance of the internal surface of the casing sections is then coated with a layer of epoxy resin which is allowed to polymerize. Thereafter the sections and rotor assembly are reassembled in the operating condition.

In the preferred embodiment, the thickness of the epoxy resin layer in the ring recesses in the final condition is approximately A inch thick.

Reference to the drawing will further explain the invention wherein:

FIG. 1 is a top plan view of the lower section of a pump casing showing recesses and rotor shaft recesses cast in an oversized condition.

FIG. 2 is a view similar to FIG. 1, but showing the ring recesses and rotor shaft recesses initially coated with layers of unpolymerized epoxy resin.

FIG. 3 is a view similar to FIG. 2, but showing the rotor assembly mounted in the rotating position in the lower section and with spacer elements spaced around the gasket area of the section.

FIG. 4 is a side elevation view of the lower section shown in FIGS. 1-3, and also showing the upper section of the pump casing mounted thereon, and drawn together or pressed together by bolt means.

FIG. 5 is a view similar to FIG. 3, showing the top section of the casing housing removing and showing the balance of the internal surface of the lower section of the casing having a layer of epoxy resin added thereto.

Referring now to FIG. 1, the numeral 11 is used to generally designate the lower section of a centrifugal pump case. This particular pump is provided with annular nange 12, forming inlet means to the pump casing. Section 11 also has a pair of webs 13 which webs mate with similar webs in the top section of the pump casing to form two partition walls in the casing. Each of the webs 13 is provided with a semi-annular recess 14 which mates with similar recesses in the webs of the top section of the casing to form annular openings in the partition walls, which openings receive the rotor assembly in the assembled condition.

In addition, each end of casing section 11 is provided with a rotor shaft recess 15 which mate with similar recesses in the top section of the casing, and which recesses are coaxially aligned with recesses 14.

It is to be understood that the pump casing is also provided with inlet means (not shown) which admit fluid to end chambers 17 and 18 provided in the casing and that the fluid being pumped passes axially through portions of the rotor assembly mounted in recesses 14 and thence outwardly through the opening at flange 12 by operation of the rotor assembly.

It is to be further understood that recesses 14 and 15 are initially cast to oversized dimensions, as are the mating recesses in the top section of the casing housing. The openings formed by these recesses are preferably about /2 inch larger in diameter in the assembled condition than the diameter of the portion of the rotor assembly received thereinto.

As shown in FIG. 2, recesses 14 and 15 of easing section 11 and the corresponding recesses of the top section of the casing are each provided with a layer of unpolymerized epoxy resin, with the thickness of the layers being greater than the radial distance between the recesses and the outside circumference of the portion of the rotor assembly to be received therein. Recesses 14 are shown having built-up layers of unpolymerized epoxy and recesses 15 are shown with layers 21 of the same material. It is to be understood that these layers can be initially peaked, but it is important that the initial thickness be greater than will be the distance between the recesses and that portion of the rotor assembly to be mounted therein.

The rotor assembly, generally designated by the arrow 25 in FIG. 3, is then placed in the rotating position in the casing section 11 as shown. In this particular embodiment the rotor assembly includes a shaft 26, one end of which is connected for rotation by any convenient power source, and is provided with sealed bearings 27 at each end of casing 11, which bearings are received in recesses 15.

In addition, shaft 26 has mounted thereon rotor blades 28 which are spaced between a pair of wear rings 29 having vanes therein for axial movement of fluid therethrough. Wear rings 29 are adapted for rotation inside of and in close fitting relationship with casing rings 30 which are mounted in recesses 14 in a stationary position. Though casing rings 30 do not rotate, they are considered part of the rotor assembly for purposes of this description. It is to be understood that the rotor assembly is generally made of a non-corrosive type material such as stainless steel or the like.

It will be observed that the top outside edge 23 of the casing section 11 is generally fiat and adapted to receive a gasket thereagainst, and is also provided with a plurality of bolt holes 32 for receiving bolts for connecting the top section of the pump casing thereto.

In addition, FIG. 3 shows a plurality of spacer means loosely mounted thereon in the form gasket pieces 33. These gasket pieces are normally cut from a gasket of the type which will normally be used in assembling the pump and will be generally of the same thickness. The purpose of gasket pieces 33 is to properly space the top section of the pump casing with respect to floor section 11, as will be explained hereinafter. Since pieces 33 do not cover the entire gasket area, but only a small portion thereof, the pieces are more compressible than the full gasket, and hence, the top section of the casing housing and the lower section 11 can be drawn to a slightly closer position during the manufacturing process as will be explained hereinafter.

Referring now to FIG. 4, top section 35 of the pump casing is mounted over section 11 and bolted thereto by bolts 36 with gasket pieces 33 therebetween. As explained above, top section 35 has upper webs, which webs match webs 13 of section 11, and that these upper webs have recesses which match recesses 14 and 15 of section 11. These upper recesses will have similarly been coated with a built-up layer of unpolymerized epoxy resin as was described with respect to recesses 14 and 15 in section 11.

Sections 11 and 35 will be drawn or pressed together by operation of bolts 35, with the rotor assembly mounted therein. This thereby reduces the thickness of the epoxy layers 20 and 21 in section 11 and the matching layers in the upper recesses in section 35, to thereby reduce these layers to the desired or predetermined thickness, which is preferably about inch. The epoxy resin is then allowed to stand for approximately 6 hours or until polymerized to a hardened condition.

Thereafter section 35 is removed from section 11 and the rotor assembly 25 is removed. The balance of the interior surfaces of sections 11 and 35 are then coated as by brushing with layer 36 of epoxy resin to a thickness of approximately inch, for example. After all the epoxy resin layers have polymerized to a hardened condition, sections 11 and 35 and rotor assembly 25 are reassembled again with a full gasket between sections 11 and 35. Since the normal gasket is less compressible than gasket pieces 33, by a few thousands of an inch, rings 30 are provided with a very small tolerance for fitting into the polymerized layers of resin coating recesses 14.

Since casing rings 30 have an outside diameter of approximately /2 inch less than the outside diameter of the openings formed by recesses 14, the layer of resin covering recesses 14 will be approximately inch thick.

It will thus be apparent that the art is provided with a method of coating the entire internal surface of the casing of a cenrifugal pump with a coating of epoxy resin to thereby eliminate the corrosive problems described above. This method eliminates the necessity for milling the ring recesses to the desired configuration and easily adapts a particular rotor assembly to a particular pump casing. In addition, the entire internal surface of the cast iron casing, including the ring recesses, is provided with an epoxy coating which eliminates the corrosive action described above. Moreover, the milling work required to size the recess openings to fit the particular rotor which is to be mounted therein is eliminated, thereby saving time and money in the manufacture of the pumps. The pumps thus coated have a much longer usable life than noncoated pumps or pumps which are not entirely coated over all the internal surface of the casing.

Further modifications may be made in the invention as described without departing from the scope thereof. Accordingly, the foregoing description is to be construed as illustratively only and is not to be considered as a limitation upon the invention as defined in the following claims.

What is claimed is:

1. The method of manufacturing a centrifugal pump casing having a layer of corrosive resistant material covering the entire internal surface of said casing, wherein said pump casing has upper and lower sections made of cast iron, each of said sections having at least one semiannular recess, which recesses together form an annular opening in the assembled condition and wherein said casing is arranged for reception therein of a rotor assembly a portion of which is adapted to be received in said annular opening in the assembled condition, said method comprising the steps of:

casting said upper and lower sections with oversized semi-annular recesses; initially coating each of said semi-annular recesses with a layer of unpolymerized epoxy resin, said layers being of a thickness greater than the radial distance between said annular opening and said portion of said rotor assembly in the assembled condition;

placing said rotor assembly in one of said sections of said casing in the rotating position, and mounting the other one of said sections of said casing over said rotor, with spacing means between said sections;

drawing said sections of said casing together against said spacing means, thereby pressing said layers of epoxy resin to the desired thickness;

separating said sections of said casing after said epoxy resin has polymerized to a hardened condition;

and coating the balance of the internal surface of said casing sections with a layer of polymerized epoxy resin.

2. The method as claimed is claim 1 wherein:

said upper and lower sections are cast with oversized semi-annular recesses, which recesses together form said annular opening having a diameter about /2 inch larger than the outside diameter of said portion of said rotor assembly which is received therein in the assembled condition;

and wherein each of said layers of unpolymerized epoxy resin initially coated in said recesses is substantially more than inch in thickness.

3. The method as claimed in claim 2 wherein:

the layer of epoxy resin coating the balance of the internal surfaces of said casing sections is at least about 3/10 inch in thickness.

4. The method of manufacturing a centrifugal pump casing having a layer of corrosive resistant epoxy resin covering the entire internal surface of the said casing, wherein said pump casing has upper and lower sections made of cast iron, each of said sections having at least two webs, which webs in the assembled condition of said sections form two partition walls in said casing, and which webs are each provided with a semi-annular recess, with the recess in one section mating with the recess of another section in the assembled condition, whereby an annular opening is provided in each of said partition walls, and wherein said casing is arranged for reception therein of a rotor assembly having at least two casing rings, one of which is adapted to be received in each of said annular openings, said method comprising the steps of:

casing said upper and lower sections with oversized semi-annular recesses; initially coating each of said semi-annular recesses with a layer of unpolymerized epoxy resin, each of said layers being of a thickness greater than the radial distance between said recesses and the outside circumference of said casing ring to be received therein;

placing said rotor assembly, including said casing rings, in one of said sections in the rotating position, and mounting the other one of said sections over said rotor assembly;

pressing said sections together to thereby reduce the thickness of said epoxy layers in said recesses to a predetermined thickness;

separating said sections of said casing after said epoxy resin has polymerized to a hardened condition;

and coating the balance of the internal surface of said casing sections with a layer of polymerized epoxy resin.

5. The method as claimed in claim 4 wherein:

each pair of mating recesses in said upper and lower sections form an annular ring having a diameter about A inch larger than the outside diameter of said casing ring received therein, whereby the thickness of said layer of epoxy covering said recesses is about A inch thick in the radial direction.'

6. The method as claimed on claim 4 wherein:

said layers of unpolymerized epoxy covering said recesses are reduced to said predetermined thickness by placing spacer means between said sections when said sections are pressed together.

References Cited UNITED STATES PATENTS 2,422,412 6/1947 Van Der Merwe Haarhoff. 2,850,999 9/1958 Kaplan et a1 29-528 X 3,155,045 11/1964 Lown et a1. 1031 14 X 3,290,199 12/1966 Willhoite 264 X 3,354,537 11/1967 OConnor 29156.4 X

JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner US. Cl. X.-R. 

